Tuberculosis

This section covers such aspects of TB treatment in HIV-infected persons as side effects and drug-drug interactions once a diagnosis of an active TB disease has been established. More information will be available on TB epidemiology, TB aetiology and pathogenesis, TB diagnostic precedures and clinical presentation of TB.

Tuberculosis (or TB) is a disease caused by a bacterium called Mycobacterium tuberculosis. This disease usually affects the lungs, but TB bacteria can attack any organ of the body, most commonly the kidney, spine, and brain. If left untreated or not treated properly, TB disease can be fatal within 5 years in 50-65% of cases.

HIV infection is the greatest risk factor for development of active TB disease throughout the course of HIV disease, including after ART initiation [ref Havlir]. Therefore, all HIV patients should be regularly screened for TB, especially in TB endemic settings and in high-risk groups (ie, injecting drug users).

Treatment of active TB disease

 

All HIV patients with a TB diagnosis, either definite (where mycobacteria tuberculosis were identified) or presumptive (clinical symptoms and history suggestive for TB [link to El Saadr article]) should start TB treatment as soon as possible.

If an HIV patient with TB is not yet receiving combination antiretroviral therapy (cART), it is recommended to first start TB treatment [ref] and then introduce cART. The time of cART introduction depends on the patient's immune status (level of CD4 cell count), but it generally should be within 2-8 weeks of initiation of TB treatment. [ref CDC and BHIVA guidelines].

The treatment of active TB has two aims:

  • for an individual - to cure the patient with TB and thereby prevent mortality
  • for public health - to interrupt TB transmission to other people by killing Mycobacteria and rendering patients noninfectious.

For a health care provider treating TB patients, it is important to remember public health responsibility. This includes not only prescribing an appropriate treatment regimen but also convincing patients to take their medications as prescribed, assessing the adherence of the patient to the regimen and addressing poor adherence when it occurs. By so doing, the provider will be able to better ensure adherence to the regimen until treatment is completed [ref].

All TB cases where multiple drug resistance (MDR) is not suspected should be treated with the combination of four of the first-line anti-TB drugs.

  • rifampin (RIF)
  • isoniazid (INH)
  • pyrazinamide (PZA)
  • ethambutol (EMB) or
  • styreptomycine (STR)*

More information on treatment regimens and dosages will soon be available.

For HIV infected patients, daily (or at least 5 times per week) treatment under Directly Observed Therapy (DOT) is recommended whenever possible.

Treatment consists of an initial phase of at least 2 months with 4 drugs (RIF+INH+ EMB+PZA) followed by a continuation phase of at least 4 month with 2 drugs (RIF+INH).

Sometimes it is necessary to extend treatment (e.g. in case of disseminated TB or TB meningitis, or MDR-TB) or modify the regimen due to special circumstances (e.g. HIV infection, pregnancy, children).

It is important to remember that only a combination of several drugs can effectively treat TB because Mycobacteria tuberculosis can rapidly develop resistance to a single drug or an inappropriate drug combination.

In most cases HIV-infected persons with TB should be treated in the same way as non-HIV-infected persons with TB. However, when ART is co-administrated, it is important to bare in mind drug-drug interactions and possible dose-adjustments of both anti-TB and anti-HIV drugs.

Side effects of the TB drugs
TB drugs (as any other medications) can cause side effects, some of them can be mild and easy to manage, and some of them can be severe. As TB treatment is given as a combination of several drugs, sometimes it can be difficult to determine which drug caused a particular side effect and therefore discontinuation of all drugs might be nessessary.

A summary of the most common side effects of TB drugs can be found on the attached table (pdf 40kb). Detailed side effect profiles for each drug and its management will soon be available.

How to restart TB drugs once they have been stopped due to side effects
In an instance where all TB drugs are stopped, they should be re-started one by one, starting with the least suspected drug and then introducing the remaining drugs at 2-3 day intervals. It is common to start with RIF, as this is the most important drug and also the least toxic. If the side effect reoccurrs, the last drug added should be stopped. For details please refer to the CDC guidelines.

Photo courtesy of KrzystofM at pl.wikipedia